JP6883208B2 - Image forming device and image forming program - Google Patents

Description

The present invention relates to an image forming apparatus and an image forming program.

Patent Document 1 includes an image forming unit provided inside and a sensor for reading an image formed in the image forming unit, and adjusts the gradation characteristic of the image forming unit based on the reading result of the sensor. In the image forming apparatus, the image forming unit forms a predetermined gradation patch pattern image on the transfer paper and outputs the image, and forms the image forming unit on the transfer paper, and forms the sensor on the image forming unit. Based on the output value of the sensor obtained by reading and outputting the gradation patch pattern image and the color measurement value of the gradation patch pattern image formed on the transfer paper. Therefore, an image forming apparatus including a control unit for correcting the reading characteristics of the sensor is disclosed.

Japanese Unexamined Patent Publication No. 2005-43617

The image forming apparatus may correct the amount of toner that forms an image so that the density of the image formed on the paper approaches a specified density.

When correcting the amount of toner loaded, the reading characteristics of the density sensor that reads the density of the image before it is transferred to the paper, for example, the density of the image formed on the intermediate transfer belt, are measured after the image is transferred to the paper. It may be corrected based on the measured color measurement value.

However, the toner containing white toner, clear toner, and metal pigment (hereinafter referred to as "special color toner") is a toner different from the special color toner, particularly a toner of a so-called process color such as yellow, magenta, cyan, and black. The correlation between the density measured on the paper and the amount of toner loaded on the paper is lower than that of the above. Therefore, it is not preferable to use the density of the special color toner measured on the paper for correcting the reading characteristic of the density sensor that reads the density of the image before the paper transfer from the viewpoint of correction accuracy.

According to the present invention, it is possible to correct the density value of the special color toner or the target value of the density value of the special color toner by a measuring means for measuring the density value of the image before the transfer of the paper without measuring the density value of the special color toner on the paper. It is an object of the present invention to provide an image forming apparatus and an image forming program capable of performing the same.

In order to achieve the above object, the invention of the image forming apparatus according to claim 1 is a measurement for measuring the density value of an image formed of a non-white colored toner containing no metal pigment and before being transferred to paper. The amount of the colored toner loaded using the means, the first density value of the image of the colored toner measured by the measuring means, and the second density value of the image of the colored toner transferred to the paper. The acquisition means for acquiring the correction amount of the first density value of the image of the colored toner measured by the measuring means or the correction amount of the target value of the first density value, and the colored toner acquired by the acquisition means. Corrects the density value measured by the measuring means or the target value of the density value of the image formed of the special color toner which is one of the white toner, the clear toner, and the toner containing the metal pigment. It is provided with a correction means.

In the invention according to claim 2, the correction means measures a correction amount for the colored toner acquired by the acquisition means when an image formed of the special color toner is measured by the measuring means, and a reading error of a density value occurs. Is converted into a correction amount to be corrected, and the density value measured by the measuring means of the image formed by the special color toner or the target value of the density value is corrected by using the correction amount for the special color toner.

According to the third aspect of the present invention, the acquisition means has a first reading characteristic showing a correspondence relationship between the density value of the image of the colored toner measured by the measuring means and the amount of the colored toner loaded on the paper. And the correction amount for the colored toner is acquired from the difference from the second reading characteristic indicating the correspondence relationship provided in advance by the measuring means.

In the invention according to claim 4, the measuring means measures the density value of the image from the intensity of the reflected light reflected by the image, and the acquiring means measures the measured by the specular reflection component and the diffuse reflection component of the reflected light. The correction amount for the colored toner is obtained by using the difference between the first reading characteristic and the second reading characteristic in which the density of the image measured by the means is normalized.

The invention according to claim 5 includes a detecting means for detecting the amount of the colored toner loaded on the image transferred to the paper.

According to the invention of claim 6, the correction means corrects the special color toner obtained by multiplying the correction amount for the colored toner measured by the measuring means by a predetermined coefficient according to the type of the special color toner. The amount is used to correct the output value of the measuring means with respect to the density of the image formed with the special color toner or the output value of the measuring means with respect to the target value of the density value of the image formed with the special color toner.

The invention according to claim 7 is provided with a plurality of the measuring means, the acquiring means acquires the correction amount for the colored toner measured by the measuring means for each measuring means, and the correcting means measures the measurement. Correction for the special color toner for each measurement means obtained by multiplying the correction amount for the colored toner measured for each means by a predetermined coefficient according to the type of the special color toner measured for each of the measuring means. Using the amount, the output value of the measuring means with respect to the density of the image formed with the spot color toner measured, or the output value of the measuring means with respect to the target value of the density value of the image formed with the spot color toner measured. It is corrected for each measuring means.

The invention of the image forming program according to claim 8 causes a computer to function as an acquisition means and a correction means of the image forming apparatus according to any one of claims 1 to 7.

According to the inventions of claims 1, 2 and 8, the density value of the special color toner or the special color toner by a measuring means for measuring the density value of the image before transfer to the paper without measuring the density value of the special color toner on the paper. It has the effect of being able to correct the target value of the concentration value.

According to the invention of claim 3, it is necessary to acquire the correction amount of the colored toner as compared with the case of acquiring the correction amount of the colored toner without comparing with the second reading characteristic provided in advance as a reference. It has the effect of shortening the time.

According to the invention of claim 4, the density value of the toner in the measuring means is compared with the case where the density value of the image is measured by the measuring means without separating the reflected light into the specular reflection component and the diffuse reflection component. It has the effect of improving the measurement accuracy.

According to the invention of claim 5, each time the amount of colored toner loaded on the paper is detected, the amount of colored toner loaded is detected by using an external detection means not included in the image forming apparatus. Therefore, it has the effect that the time required for detection can be shortened.

According to the invention of claim 6, the measuring means is used as compared with the case where the correction amount of the density value of the spot color toner measured by the measuring means is set for all the colors of the spot color toner. It has the effect of improving the correction accuracy of the density value of the spot color toner or the correction accuracy of the target value of the density value of the spot color toner.

According to the invention of claim 7, the correction amount of the toner density value corresponding to each color is compared with the case where the correction amount of the toner density value corresponding to each color is sequentially determined by using one measuring means. It has the effect that the time required for making a decision can be shortened.

It is a schematic side view which shows the example of the structure of the main part of an image forming apparatus. It is a figure which shows an example of a density sensor. It is a figure which shows the example of the composition of the main part of the electric system of an image forming apparatus. It is a flowchart which shows an example of the flow of the density sensor correction processing. It is a figure which shows an example of a concentration TMA characteristic. It is a schematic diagram explaining the acquisition method of the correction amount of the sensor value in a density sensor. It is a figure which shows the density control example of the colored toner using the correction amount. It is a schematic diagram explaining the acquisition method of the correction amount of the sensor value in the density sensor with respect to the spot color toner. It is a figure which shows the example of reading the density | concentration of a patch by a plurality of density sensors.

Hereinafter, the present embodiment will be described with reference to the drawings. The components and processes having the same function are given the same code throughout the drawings, and duplicate description is omitted.

Regarding the color display, yellow is represented by "Y", magenta is represented by "M", cyan is represented by "C", black is represented by "K", white is represented by "W", and transparent (clear) color is represented by "CR". Among the colors containing metallic pigments and exhibiting metallic luster, silver is represented by "S", gold is represented by "GL", red is represented by "R", green is represented by "G", and blue is represented by "B".

When it is necessary to explain each member or image separately for each color, the color code (Y, M, C, K, W, CR, S, GL, R, corresponding to each color is added to the end of the name or code. G, B) are added to distinguish. On the other hand, when each member or image is described collectively without distinguishing each member or image, the color code added to the end of the name or code is omitted.

FIG. 1 shows an example of a schematic side view showing a main configuration of an image forming apparatus 200 using an electrophotographic method. The image forming apparatus 200 is equipped with an image forming function of receiving image data via, for example, a communication line (not shown) and forming an image based on the received image data on a recording medium such as paper.

The image forming apparatus 200 includes six photoconductors 1S, 1Y, 1M, 1C, 1K, and 1CR that rotate in the direction of arrow A in the drawing for each color of S, Y, M, C, K, and CR. It includes chargers 2S, 2Y, 2M, 2C, 2K, and 2CR that charge the surface of each photoconductor 1 by supplying a charging bias.

Further, the image forming apparatus 200 exposes the surface of the charged photoconductor 1 with light modulated based on the image information of each color, and forms an electrostatic latent image on the photoconductor 1. Laser output units 3S, 3Y, 3M 3C, 3K, and 3CR, and developing rolls 34S, 34Y, 34M, 34C, 34K, and 34CR to which a developer (toner) of a color corresponding to the surroundings is attached and come into contact with the photoconductor 1 while rotating are provided, respectively. ..

The developers 4S, 4Y, 4M, 4C, 4K, and 4CR supply toner to the developing rolls 34 of the corresponding colors, and develop the developing bias by supplying the developing bias to each developing roll 34 from a developing bias power supply (not shown). The toner adhering to the roll 34 is electrostatically adhered to the electrostatic latent image, the electrostatic latent image is developed with the toner of each color, and an image is formed on the photoconductor 1. The toner is stored in a toner cartridge (not shown) prepared for each color, and the control unit 60 controls a dispense unit (not shown) to transfer the toner stored in the toner cartridge to the developer 4 of the corresponding color. To do.

As the toner, in addition to the toner, for example, a two-component toner containing a carrier which is a magnetic particle as a medium for transporting the toner is used, but a one-component toner containing no carrier may be used.

Further, the image forming apparatus 200 includes primary transfer devices 5S, 5Y, 5M, 5C, 5K, and 5CR that transfer an image of each color formed on the photoconductor 1 to the intermediate transfer belt 6 as an example of the intermediate transfer body.

Further, the image forming apparatus 200 is transferred to the paper P, the paper accommodating portion T for accommodating the paper P which is an example of the recording medium, the secondary transfer device 7 for transferring the image on the intermediate transfer belt 6 to the paper P, and the paper P. A fixing device 9 for fixing the image to the paper P and a belt cleaner 8 for removing the toner remaining on the surface of the intermediate transfer belt 6 after the image is transferred to the paper P by the secondary transfer device 7 are provided.

Further, the image forming apparatus 200 includes a cleaner (not shown) that cleans the surface of each photoconductor 1 and a static eliminator (not shown) that removes residual charges on the surface of each photoconductor 1.

Further, the image forming apparatus 200 has a density sensor 15 that reads the density of the image transferred to the intermediate transfer belt 6 for each toner color, and an image (fixed image) fixed on the paper P by the fixing device 9 per unit area. An image reading sensor 16 for measuring the amount of toner (Toner Mass per Area: TMA) for each toner color is provided. The image reading sensor 16 is an example of the detecting means.

The density sensor 15 is an example of a measuring means for measuring the density value of an image before being transferred to the paper P for each toner color. Therefore, it is not always necessary to measure the density of the image transferred to the intermediate transfer belt 6 with the density sensor 15, and the density of the image before being transferred to the paper P may be measured. For example, the density sensors 15 are installed at positions facing the image forming surface of the photoconductor 1 corresponding to each toner color, and each density sensor 15 reads the density of the image formed on each photoconductor 1. You may.

The image reading sensor 16 measures the TMA in the fixed image for each toner color by measuring the color of the image (referred to as “color measurement”). Further, the image reading sensor 16 may be provided inside the image forming apparatus 200, or may be prepared separately from the image forming apparatus 200. There are no restrictions on the color expression method measured by the image reading sensor 16, and the density, RGB value, or ^{L *} a ^* b ^* value that represents the color using ^{the density L *} and chromaticity a ^* and b ^{* for each CMYK.} Is used.

Among the image forming apparatus 200, the members related to the formation of the image transferred to the intermediate transfer belt 6, for example, the photoconductor 1, the charging device 2, the laser output unit 3, the developing device 4, and the developing roll 34 cooperate with each other. This is an example of an image forming unit 17 that forms an image on the intermediate transfer belt 6.

In the example of FIG. 1, the image forming unit 17S, the image forming unit 17Y, the image forming unit 17M, the image forming unit 17C, the image forming unit 17K, and the image are sequentially formed from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6. Although the forming unit 17CR is mounted, the color of the image formed by the image forming apparatus 200 is not limited to this.

For example, special color toner, which is a toner containing white toner, clear toner, and metal pigment, is used for color expression, image decoration, base, and coating, which are difficult to realize by combining process colors. , There are cases where it is desired to change the color of the special color toner required for forming an image according to the image. Therefore, the color of the image formed by the image forming unit 17 may be changed according to the color information included in the image.

For example, instead of the image forming units 17S and 17CR that form images of the toner color S and the toner color CR, an image forming unit 17 that forms an image of another toner color such as the toner color GL and the toner color W may be used. Needless to say, the number of image forming units 17 in the image forming apparatus 200 and the order of arrangement of the image forming units 17 are not limited to the example of FIG.

Among the toners used in the image forming apparatus 200, toners other than the spot color toners are referred to as "colored toners". Therefore, the toner colored in each color of YMCK is an example of colored toner.

Next, the image forming operation in the image forming apparatus 200 shown in FIG. 1 will be described.

First, for example, image data corresponding to an image to be image-formed is output to the image forming apparatus 200 from an external device such as a personal computer (not shown) via a communication line (not shown).

When an image is input to the image forming apparatus 200, the image forming apparatus 200 supplies a charging bias to the charging device 2 to charge the surface of the photoconductor 1 to the negative electrode.

On the other hand, the image is input to the control unit 60 of the image forming apparatus 200. The control unit 60 decomposes the input image into image data corresponding to each color component of the toner of the mounted image forming unit 17, and then converts a modulation signal based on the image data of each color into a laser of the corresponding color. Output to output unit 3. The laser output unit 3 outputs the laser beam 11 modulated according to the input modulation signal.

Each of the modulated laser beams 11 irradiates the surface of the photoconductor 1. The surface of the photoconductor 1 is in a state of being charged to the negative electrode by the charger 2, but when the surface of the photoconductor 1 is irradiated with the laser beam 11, the charge of the portion irradiated with the laser beam 11 disappears, and the photoconductor 1 is charged. Electrostatic latent images corresponding to the image data of each color are formed on the 1.

The developer 4 of each color is provided with toner charged on the negative electrodes of S, Y, M, C, K, and CR, and a developing roll 34 for adhering each toner to the surface of the photoconductor 1.

When the electrostatic latent image formed on the rotationally driven photoconductor 1 reaches the developing roll 34, a developing bias is supplied to the developing roll 34 by a developing bias power supply (not shown). As a result, the toner of each color adhering to the peripheral surface of each of the developing rolls 34 adheres to the electrostatic latent image of the photoconductor 1 of the corresponding color, and the image data decomposed into each color is attached to each of the photoconductors 1. The corresponding images are formed respectively.

Further, the rollers 12A, 12D, 12E, and the backup roll 7A of the secondary transfer device 7 are rotated by a motor (not shown), so that the intermediate transfer belt 6 is conveyed in the direction of the arrow 14, and the primary transfer device 5 and the photoconductor 1 are conveyed. The intermediate transfer belt 6 is pressed against the photoconductor 1 at each of the nip portions formed by the above. At this time, a primary transfer bias is supplied to the primary transfer device 5 from a primary transfer bias power supply (not shown), and the toner images of each color formed on the photoconductor 1 are transferred to the intermediate transfer belt 6 (primary transfer).

In the photoconductor 1 on which the toner image is transferred to the intermediate transfer belt 6, deposits such as residual toner adhering to the surface of the photoconductor 1 are removed by a cleaner (not shown), and residual charges are removed by a static eliminator (not shown).

On the other hand, the secondary transfer device 7 includes a backup roll 7A and a secondary transfer roll 7B for tensioning the intermediate transfer belt 6, and the secondary transfer roll 7B comes into contact with the intermediate transfer belt 6 to contact the intermediate transfer belt 6. It rotates following the transport of 6.

Further, when the paper transport roller 13 is rotated by a motor (not shown), the paper P in the paper accommodating portion T is formed by the secondary transfer roll pair obtained by combining the backup roll 7A and the secondary transfer roll 7B of the secondary transfer device 7. It is conveyed to the formed secondary transfer nip.

Then, when the paper P is pressed against the intermediate transfer belt 6 in a state of facing the surface of the intermediate transfer belt 6 on which the image is formed in the secondary transfer nip portion, the secondary transfer roll is supplied from the secondary transfer bias power supply. A secondary transfer bias is supplied to the pair, and the image formed on the intermediate transfer belt 6 is transferred to the paper P (secondary transfer). The image transferred on the paper P is heated and pressurized by the fixing device 9 and fixed on the paper P.

The intermediate transfer belt 6 on which the toner image is transferred to the paper P is removed by the belt cleaner 8 from deposits such as residual toner adhering to the surface.

As described above, the image is formed on the paper P, and the image forming operation is completed.

The image forming apparatus 200 executes an image forming condition adjusting process in order to bring the density of the image formed on the paper P closer to the designated density. In the image formation condition adjustment process, a density correction image (patch) having a predetermined density is formed on the intermediate transfer belt 6 for each image forming unit 17, and patches of each toner color formed on the intermediate transfer belt 6 are formed. The density of the image is adjusted by adjusting the toner amount of the image corresponding to the predetermined density for each image forming unit 17 according to the difference between the density of the patch read by the density sensor 15 and the predetermined density of the patch. The process of correction.

Specifically, the image forming apparatus 200 is supplied from, for example, a charging bias applied to the charging device 2, a developing bias applied to the developing roll 34, a laser irradiation amount (exposure amount) by the laser output unit 3, and a developing device 4. The amount of toner in the image is adjusted by adjusting the toner concentration of the toner (mixing ratio of carrier and toner) and the like. The adjustment item used for adjusting the toner amount of the image by the image formation condition adjustment process is referred to as "image formation condition". That is, the charging bias and the like illustrated above are examples of image forming conditions.

FIG. 2 is a diagram showing an example of a density sensor 15 that reads the density of the patch 10 formed on the intermediate transfer belt 6.

The density sensor 15 is a sensor that optically reads the density of the patch 10 transported in the transport direction of the intermediate transfer belt 6 indicated by the arrow 14 together with the intermediate transfer belt 6. The density sensor 15 includes a light emitting element 15-1 that irradiates light, and a light receiving element 15-2 that receives the reflected light reflected by the patch 10 among the light emitted from the light emitting element 15-1. The density sensor 15 identifies the color of the patch 10 from the wavelength of the reflected light received by the light receiving element 15-2, and controls a value (sensor value) according to the density of the patch 10 from the intensity of the received reflected light. Output to 60.

Hereinafter, the density sensor 15 will be described as a deflection separation type density sensor 15 that separates the reflected light into a specular reflection component and a diffuse reflection component and reads the density of the patch 10, but separates the reflected light into each component. There may be a method of reading the density of the patch 10.

In the density sensor 15, the light emitting characteristics of the light emitting element 15-1 and the light receiving characteristics of the light receiving element 15-2 may differ for each density sensor 15 due to individual differences of the so-called density sensor 15, so that the sensor value for the same patch 10 is obtained. May be different for each density sensor 15.

Further, the sensor value for the same patch 10 is different for each density sensor 15 due to the difference in the mounting state of the density sensor 15 such as the mounting angle of the density sensor 15 with respect to the intermediate transfer belt 6 and the distance from the intermediate transfer belt 6 to the density sensor 15. It may be different.

Further, even if the density sensor 15 is the same, the sensor value of the density sensor 15 for the same patch 10 may be increased due to toner stains on at least one of the light emitting surface of the light emitting element 15-1 and the light receiving surface of the light receiving element 15-2. May change.

Therefore, in the image forming apparatus 200, the image forming condition of the patch 10 is controlled so that the density of the patch 10 read by the density sensor 15 approaches a predetermined density, and then the patch 10 formed on the paper P is used by the image reading sensor. The color is measured in No. 16, and the TMA of the patch 10 obtained from the color measurement result is used to correct the density value read by the density sensor 15 and the target value of the density value. As a result, the reading error of the density value in the density sensor 15 is corrected.

Here, since a correlation is seen between the TMA of the patch 10 formed of the colored toner and the color measurement result of the image reading sensor 16, the TMA can be obtained from the color measurement result of the patch 10. However, the correlation between the TMA of the patch 10 formed of the spot color toner and the color measurement result of the image reading sensor 16 tends to be weaker than that of the patch formed of the spot color toner.

For example, among the spot color toners, the white toner has the same color as the ground color of the paper P, and the clear toner transmits the ground color of the paper P. Therefore, the image reading sensor 16 measures the change in the TMA of the patch 10. There is no big difference in the change in color result. Further, among the spot color toners, the toner containing a metal pigment causes a difference in the color measurement result of the image reading sensor 16 regardless of the TMA of the patch 10 depending on the position and orientation of the metal pigment on the paper. Further, regarding the index indicating the metallic glossiness of the toner containing the metal pigment among the spot color toners, when the TMA of the patch 10 is less than the threshold value, the index increases as the TMA increases, but the TMA of the patch has a threshold value. When the above is reached, the index becomes smaller.

That is, it is more difficult to obtain the TMA of the spot color toner more accurately from the color measurement result of the patch 10 formed on the paper P than the TMA of the colored toner. Therefore, the correction of the density value reading error of the density sensor 15 for the image formed of the special color toner is more difficult than the correction of the density value reading error of the image formed of the colored toner.

Therefore, the image forming apparatus 200 executes the density sensor correction process described later, so that the density sensor 15 does not measure the density of the special color toner patch 10 on the paper P, and the density sensor 15 reads the special color toner or the special color toner. Correct the target value of the reading density value of.

Next, with reference to FIG. 3, the configuration of a main part of the electrical system of the image forming apparatus 200 will be described.

As shown in FIG. 3, the control unit 60 of the image forming apparatus 200 is composed of, for example, a computer 50. The computer 50 includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a non-volatile memory 54, and input / output, which are examples of the acquisition means and the correction means according to the present embodiment. It includes an interface (I / O) 55. The CPU 51, ROM 52, RAM 53, non-volatile memory 54, and I / O 55 are each connected via the bus 56.

Further, the I / O 55 includes a primary transfer device 5, a secondary transfer device 7, a fixing device 9, a density sensor 15, an image reading sensor 16, each image forming unit 17 corresponding to each toner color, and a transport motor group. 18 is connected.

Among these, the transfer motor group 18 includes various rollers (for example, rollers 12A, 12D, 12E) that transfer the intermediate transfer belt 6, and motors that drive the paper transfer rollers 13 and the like that convey the paper P.

The device connected to the I / O 55 is not limited to the device illustrated in FIG. For example, it may be connected to a communication line such as the Internet, and a communication device for transmitting and receiving data may be connected to an external device connected to the communication line.

Next, with reference to FIG. 4, the operation of the image forming apparatus 200 for correcting the target value of the read density value of the spot color toner or the read density value of the spot color toner by the density sensor 15 will be described.

FIG. 4 is a flowchart showing an example of the flow of the density sensor correction process executed by the CPU 51 at any timing after the power of the image forming apparatus 200 is turned on.

The image forming program that defines the density sensor correction process is stored in advance in, for example, the ROM 52. The CPU 51 reads the image forming program stored in the ROM 52 and executes the density sensor correction process.

The CPU 51 may execute the density sensor correction process according to a predetermined interval, or may execute the density sensor correction process according to a user's start instruction. Further, the CPU 51 may execute the density sensor correction process during the formation of the image instructed by the user, or may execute the density sensor correction process during the waiting period during which the image instructed by the user is not formed. When the density sensor correction process is executed during the formation of the image instructed by the user, the CPU 51 may form the patch 10 on the paper P on which the image is not formed.

It is assumed that the image forming apparatus 200 executes the image forming condition adjusting process before performing the density sensor correction processing, and adjusts the image forming condition according to the density of the image for each image forming unit 17.

First, in step S10, the CPU 51 controls the image forming unit 17 and the primary transfer device 5 corresponding to any of the colored toners to form the colored toner patch 10 on the intermediate transfer belt 6. If it is a colored toner, there is no restriction on the color of the patch 10 formed on the intermediate transfer belt 6, but it is possible to form the C color or M color patch 10 whose density difference is easier to measure than the colors of other colored toners. preferable. Here, as an example, an example of forming the patch 10 of the toner color C will be described.

In step S20, the CPU 51 causes the density sensor 15 to read the density of the toner color C patch 10 formed on the intermediate transfer belt 6 in step S10.

In step S30, the CPU 51 stores in the RAM 53 the density read in step S20, that is, the sensor value output from the density sensor 15 according to the density of the patch 10. The sensor value stored in the RAM 53 in step S30 is an example of the first concentration value.

At this time, since the density sensor 15 separates the reflected light of the patch 10 into a specular reflection component and a diffuse reflection component and reads them, the CPU 51 normalizes the sensor value corresponding to the density of the patch 10 read in step S20. After that, it is stored in the RAM 53. Specifically, among the reflected light of the patch 10, the mirror surface reflection component is set to "mirror surface Vpatch", the diffuse reflection component is set to "diffuse Vpatch", and the reflected light measured in a state where the patch 10 is not formed on the intermediate transfer belt 6. Assuming that the mirror reflection component of the above is “mirror surface Vclean” and the diffuse reflection component is “diffuse Vclean”, the sensor value T of the density sensor 15 is expressed by Eq. (1).

(Number 1)
T = (mirror surface Vpatch-diffusion Vpatch) x 1023 / (mirror surface Vclean-diffusion Vclean) ... (1)

In the equation (1), “1023” is a reference value of the sensor value, and determines the sensor value of the density sensor 15 when the patch 10 is not formed on the intermediate transfer belt 6. The sensor value of the density sensor 15 decreases as the amount of toner in the patch 10 increases.

In step S40, the CPU 51 controls the secondary transfer device 7 at the timing when the patch 10 formed on the intermediate transfer belt 6 in step S10 is conveyed to the secondary transfer nip portion of the secondary transfer device 7, and is transferred to the paper P. Form patch 10.

In step S50, the CPU 51 controls the image reading sensor 16 to measure the color of the patch 10 formed on the paper P in step S40. As described above, there are no restrictions on the method of expressing the color measurement result in the image reading sensor 16, but here, as an example, the color of the patch 10 read by the image reading sensor 16 is represented by the density of each CMYK. In the present embodiment, since the image reading sensor 16 measures the patch 10 of the toner color C, the density of MYK for each toner color is "0", or a density that is negligible compared to the density of the toner color C. It becomes. The density of the patch 10 measured by the image reading sensor 16 is an example of the second density value.

Then, the CPU 51 acquires the density TMA characteristic corresponding to the toner color (in this case, the toner color C) of the measured patch 10 among the density TMA characteristics stored in advance for each colored toner.

FIG. 5 is a diagram showing an example of density TMA characteristics corresponding to the toner color C. The density TMA characteristic is a characteristic showing the correspondence between the density of the patch 10 formed of any one of the colored toners and the amount of the colored toner loaded, that is, the correspondence between the patch 10 and the TMA. In FIG. 5, the vertical axis represents the density of the toner color C, and the horizontal axis represents the TMA of the patch 10.

The density TMA characteristics for each colored toner are obtained in advance by, for example, an experiment using an actual image reading sensor 16 or a computer simulation based on the design specifications of the image reading sensor 16, and may be stored in the non-volatile memory 54 in advance, for example.

The CPU 51 acquires the TMA corresponding to the density of the patch 10 measured by the image reading sensor 16 with reference to the acquired density TMA characteristic, and stores the acquired TMA in the RAM 53.

In step S60, the CPU 51 acquires the correction amount of the sensor value with respect to the toner color C of the density sensor 15.

Specifically, the CPU 51 is the difference between the original sensor value that the density sensor 15 should output to the TMA of the patch 10 acquired in step S50 and the sensor value actually obtained from the density sensor 15 in step S20. Is acquired as a correction amount of the sensor value with respect to the toner color C of the density sensor 15.

FIG. 6 is a diagram illustrating a method of acquiring a correction amount of a sensor value with respect to the toner color C of the density sensor 15. In FIG. 6, the vertical axis represents the normalized sensor value (normalized density sensor output value) output from the density sensor 15 when the density of the patch 10 is read by the density sensor 15, and the horizontal axis represents the paper P. Represents the TMA of the formed patch 10.

The reference sensor characteristic is a characteristic that is preset for each density sensor 15 and for each toner color used in the image forming apparatus 200, and indicates a correspondence relationship between the normalized density sensor output value and the TMA of the patch 10. The reference sensor characteristics are, for example, the patch 10 having a predetermined TMA in a state where the density sensor 15 is mounted at the correct position as designed and the light emitting surface and the light receiving surface of the density sensor 15 are not contaminated with toner or the like. The sensor value (reference sensor value) of the density sensor 15 that is output when the density is read is shown. According to the reference sensor characteristics of FIG. 6, it is shown that the reference sensor value when the patch 10 of the toner color C having the TMA of _{H c1 is read by the density sensor 15 is Q c1.}

On the other hand, when the sensor value for the density of the patch 10 read in step S20 is Q _c3 , the sensor value of the density sensor 15 originally indicates _{Q c1} for the patch 10 of the toner color C having the TMA of _{H c1.} Therefore, (Q _c1- Q _c3 ) is the density reading error in the density sensor 15. That is, in this case, _{by adding (Q c1-} Q _c3 ) to the sensor value of the concentration sensor 15, the concentration sensor 15 shows the correct concentration. Accordingly, the correction amount E _c of the sensor values for toner color C of the density sensor 15, the difference between the sensor value for the density of the patch 10 read in step S20, the reference sensor value for the TMA in the same patch 10 obtained in step S50 It is represented by.

In FIG. 6, the characteristic of passing the sensor value actually measured by the concentration sensor 15 is also referred to as “actual measurement sensor characteristic”. Correction amount E _c of the sensor values for toner color C of the density sensor 15 in each TMA is tend to be the same regardless of the value of TMA observed. Therefore, by obtaining the correction amount E _c of the density sensor 15 for a particular TMA, by moving the reference sensor characteristics so as to pass through the actual measured sensor values by the density sensor 15 as it is in the vertical direction, the measured sensor characteristics Is estimated.

The method for estimating the measured sensor characteristics is not limited to this. The sensor value for the patch 10 of the toner color C having a different TMA may be acquired by the density sensor 15, and a curve that approximates the acquired plurality of normalized density sensor output values using, for example, the least squares method may be used as the measured sensor characteristic. .. In this case, the estimation accuracy of the measured sensor characteristics in each TMA is improved as compared with the case where the measured sensor characteristics are estimated from the sensor values for one patch 10 of the toner color C having a specific TMA. _{That is, the accuracy of the correction amount E c} of the sensor value with respect to the toner color C of the density sensor 15 is improved. Here, the actually measured sensor characteristic is an example of the first reading characteristic, and the reference sensor characteristic is an example of the second reading characteristic.

FIG. 7 is a diagram showing an example of density control of the toner color C using the _{acquired correction amount E c.} In FIG. 7, the vertical axis represents the normalized density sensor output value of the density sensor 15 with respect to the image of the toner color C, and the horizontal axis represents the TMA of the image of the toner color C formed on the paper P.

For example, if the sensor value for the image read by the density sensor 15 is a Q _c2, CPU 51 is the actual concentrations of the read image by the density sensor 15 is a value obtained by adding the correction amount E _c in Q _c2 Q _c0 It may be treated as a concentration corresponding to.

Further, when adjusting the toner amount of the image in order to form the image having the specified TMA (for example, H _c0 ) on the paper P, the CPU 51 determines that the sensor value of the density sensor 15 is the reference sensor value Q _{c0 with respect to H c1.} The image formation conditions may be adjusted so as to show _{Q c2} , which is a value smaller by the correction amount E _c. That is, the CPU 51 corrects the target value of the sensor value in the density sensor 15 in order to form an image having the designated TMA on the paper P.

Next, in step S70, the CPU 51 determines whether or not the image forming device 200 is equipped with an image forming unit 17 (spot color image forming unit 17) that forms an image using the spot color toner. When the spot color image forming unit 17 is not mounted on the image forming apparatus 200, it is not necessary to correct the target value of the reading density value of the spot color toner or the reading density value of the spot color toner in the density sensor 15, and thus is shown in FIG. The density sensor correction process is terminated.

On the other hand, when the spot color image forming unit 17 is mounted on the image forming apparatus 200, the process proceeds to step S80. In the example of the image forming apparatus 200 shown in FIG. 1, since the image forming unit 17S and the image forming unit 17CR are mounted, the determination process in step S70 becomes an affirmative determination, and the process proceeds to step S80.

In step S80, the CPU 51 selects one special color image forming unit 17 from the mounted special color image forming units 17.

In step S90, the CPU 51 acquires the color of the spot color toner corresponding to the spot color image forming unit 17 selected in step S80. Then, CPU 51 is a correction amount E _c of the sensor values for toner color C of the density sensor 15 acquired in step S60, by converting the correction amount of the sensor values for acquired features toner color, the spot color toner obtained The correction amount of the sensor value of the density sensor 15 with respect to the color is acquired.

Specifically, CPU 51, by multiplying the coefficient set in advance according to the features toner color to the correction amount E _c, obtains a correction amount of the sensor value of the density sensor 15 for the color of the spot color toners obtained.

The coefficient set according to the color of the spot color toner is obtained in advance by, for example, an experiment using an actual machine of the image forming apparatus 200 or a computer simulation based on the design specifications of the image forming apparatus 200, and is stored in advance in, for example, the non-volatile memory 54. Just leave it.

FIG. 8 is a diagram showing a flow of acquiring a correction amount of a sensor value of the density sensor 15 with respect to the color of the spot color toner. FIG. 8 shows an example of acquiring _{the correction amount E s} of the sensor value for the toner color S from _{the correction amount E c} of the sensor value for the toner color C.

When the color of the spot color toner corresponding to the spot color image forming unit 17 selected in step S80 is S color, _{the correction amount E s} of the sensor value for the toner color S is obtained from _{the correction amount E c of the sensor value for the toner color C.} The correction amount E _s is obtained by acquiring the coefficient α _cs for the purpose from the non-volatile memory 54 _{and multiplying the correction amount E c} by the coefficient α _cs.

In step S100, the CPU 51 determines whether or not there is a special color image forming unit 17 that has not yet been selected in step S80 among the special color image forming units 17 mounted on the image forming apparatus 200. Then, if there is a spot color image forming unit 17 that has not yet been selected in step S80, the process proceeds to step S80.

In the example of the image forming apparatus 200 shown in FIG. 1, the image forming unit 17CR is included, and since the image forming unit 17CR has not been selected yet, the process proceeds to step S80. Then, in step S90, CPU 51 obtains the coefficient alpha _ccr for obtaining a correction amount E _cr of the sensor values for the toner color CR from the correction amount E _c from the nonvolatile memory 54, the coefficient alpha _ccr the correction amount E _c The correction amount E _cr is obtained by multiplying.

In this way, by repeatedly executing the processes of steps S80 to S100 until the determination process of step S100 becomes a negative determination, each of the spot color image forming units 17 mounted on the image forming apparatus 200 is formed. The correction amount of the sensor value of the density sensor 15 corresponding to the color of each image is acquired.

On the other hand, when all the special color image forming units 17 mounted on the image forming apparatus 200 are selected and the determination process in step S100 becomes a negative determination, the density sensor correction process shown in FIG. 4 is terminated.

After that, when the toner color of the image read by the density sensor 15 is S color, the CPU 51 adds a correction amount E _s to the detected sensor value for the actual density of the toner color S image read by the density sensor 15. It may be treated as a concentration corresponding to the added value.

Further, when adjusting the amount of toner of the toner color S used for image formation in order to form an image of the toner color S having the designated TMA on the paper P, the CPU 51 determines the sensor value of the density sensor 15 with respect to the toner color S. but to show only a small sensor value correction amount E _s from the reference sensor value for the specified TMA, it may be adjusted imaging conditions. That is, the CPU 51 corrects the target value of the sensor value in the density sensor 15 so that the TMA of the image of the spot color toner formed on the paper P becomes the designated TMA.

As described above, the image forming apparatus 200 does not measure the color of the special color toner patch 10 formed on the paper P by the image reading sensor 16, but from the correction amount of the sensor value of the density sensor 15 corresponding to the color of the colored toner. , Acquire the correction amount of the sensor value of the density sensor 15 corresponding to each color of the special color toner.

Since the measurement accuracy of the TMA of the patch 10 formed of the special color toner in the image reading sensor 16 is lower than the measurement accuracy of the TMA of the patch 10 formed of the special color toner, it corresponds to each color of the special color toner in the image forming apparatus 200. The correction amount of the sensor value of the density sensor 15 is an accurate correction amount compared with the correction amount obtained by measuring the TMA of the patch 10 formed of the special color toner with the image reading sensor 16 and measuring the TMA. Will be shown.

That is, the image forming apparatus 200 does not read the TMA of the special color toner contained in the image formed on the paper P by the image reading sensor 16, but uses only the sensor value of the density sensor 15 to set the TMA of the special color toner as a target value. As it gets closer, the density of the image formed by the special color toner is acquired more accurately.

In the present embodiment, the image reading sensor 16 measures the color of the patch 10 formed on the paper P, but the image reading sensor 16 is not necessarily an essential sensor for the image forming apparatus 200. When the image forming apparatus 200 is not provided with the image reading sensor 16, the color of the patch 10 is measured using an external spectrophotometer, and the color is obtained by measuring the density TMA characteristics shown in FIG. The TMA of patch 10 may be obtained from the obtained concentration.

In some cases, the image forming apparatus 200 may include a plurality of density sensors 15.

FIG. 9 is a diagram showing an example of reading the density of the patch 10 by the image forming apparatus 200 provided with a plurality of density sensors 15.

In the image forming apparatus 200 provided with a plurality of density sensors 15, the color of the patch 10 read by each density sensor 15 is predetermined. For example, the density sensor 15J reads the density of the patch 10C having the toner color C and the patch 10S having the toner color S, and the density sensor 15U reads the density of the patch 10M having the toner color M and the patch 10CR having the toner color CR. Read the concentration of.

As an example, when the patch 10C and the patch 10M, and the patch 10S and the patch 10CR are formed along the direction orthogonal to the transport direction indicated by the arrow 14 of the intermediate transfer belt 6, respectively (the width direction of the intermediate transfer belt 6). When the densities of the patches 10C, patches 10S, patches 10M, and patches CR formed in a row along the transport direction of the intermediate transfer belt 6 are read by the density sensor 15 of either the density sensor 15J or the density sensor 15U. In comparison with, the time required to read the densities of all the patches 10 is shortened. Therefore, the image forming apparatus 200 including a plurality of density sensors 15 has a shorter time required for the image forming condition adjusting process than the image forming apparatus 200 including one density sensor 15.

The present invention is also applied to an image forming apparatus 200 including a plurality of such density sensors 15.

Specifically, the density sensor for the toner color M concentration sensor 15U of acquiring the correction amount E _c of the sensor values of the density sensor 15J to the toner color C by the density sensor 15J for reading the density of a patch 10C, reads the densities of the patch 10M obtaining a correction amount E _m of the sensor value of 15U.

Since the correction amount E _c is a correction amount peculiar to the density sensor 15J and the correction amount E _m is a correction value peculiar to the density sensor 15U, the CPU 51 has S color as the toner color of the image read by the density sensor 15J. If this is the case, the target value of the reading density value of the toner color S or the reading density value of the special color toner is corrected by using the correction amount E _{s obtained by multiplying the correction amount E c} by the coefficient α _cs. ..

Meanwhile, CPU 51, when the toner color of the image read by the density sensor 15U was CR colors, resulting in the correction amount E _m, multiplying the coefficient alpha _mcr for obtaining a correction amount E _cr from the correction amount E _m The target value of the reading density value of the toner color CR or the reading density value of the special color toner is corrected by using the correction amount E _cr.

That is, the CPU 51 uses the correction amount of the sensor value for the colored toner acquired for each density sensor 15, and the sensor value for the density of the image of the special color toner read by each density sensor 15, or the designated special color toner. The target value of the sensor value with respect to the density of the image is corrected for each density sensor 15.

Although the disclosed technology has been described above using the embodiments, the disclosed technology is not limited to the scope described in each embodiment. Various changes or improvements can be made to each embodiment without departing from the gist of the disclosed technology, and the modified or improved form is also included in the technical scope of the disclosed technology. For example, the order of processing may be changed without departing from the gist of the disclosed technology.

The developer 4 and the developing roll 34 corresponding to each color are housed in one rotating drum, and the developing device 4 and the developing roll 34 are switched by rotating the drum, and the target color for the common photoconductor 1 is obtained. The present invention may be applied to a rotary development type image forming apparatus for forming an image of.

Further, in the embodiment, the embodiment in which the concentration sensor correction process in the control unit 60 is realized by software has been described as an example, but for example, the process equivalent to the flowchart shown in FIG. 4 may be processed by hardware. Good. In this case, the processing speed can be increased as compared with the case where the processing in the control unit 60 is realized by software.

In the above-described embodiment, the embodiment in which the image forming program is installed in the ROM 52 has been described, but the present invention is not limited to this. The image forming program according to the present invention can also be provided in a form recorded on a computer-readable recording medium. For example, the image forming program according to the present invention may be provided in a form recorded on an optical disk such as a CD (Compact Disc) -ROM or a DVD (Digital Versatile Disc) -ROM. Further, the image forming program according to the present invention may be provided in a form recorded in a semiconductor memory such as a USB memory and a flash memory. Further, when the communication device is connected to the image forming device 200, the image forming program according to the present invention may be acquired from another external device via the communication line.

1 (1Y, 1M, 1C, 1K, 1S, 1CR) ... Photoconductor 2 (2Y, 2M, 2C, 2K, 2S, 2CR) ... Charger 3 (3Y, 3M, 3C, 3K, 3S, 3CR) ... Laser output unit 4 (4Y, 4M, 4C, 4K, 4S, 4CR) ... Developer 5 (5Y, 5M, 5C, 5K, 5S, 5CR,) ... Primary transfer device 6.・ ・ Intermediate transfer belt 7 ・ ・ ・ Secondary transfer device 8 ・ ・ ・ Belt cleaner 9 ・ ・ ・ Fixer 10 (10M, 10C, 10S, 10CR) ・ ・ ・ Patch 15 (15J, 15U) ・ ・ ・ Density sensor 16 ... Image reading sensor 17 (17Y, 17M, 17C, 17K, 17S, 17CR) ... Image forming unit 34 (34Y, 34M, 34C, 34K, 34S, 34CR) ... Development roll 50 ... Computer 51 ... CPU
60 ... Control unit 200 ... Image forming device P ... Paper

Claims (8)

A measuring means for measuring the density value of an image before being transferred to paper, which is formed of a non-white colored toner containing no metal pigment.
Using the first density value of the image of the colored toner measured by the measuring means and the second density value of the image of the colored toner transferred to the paper, the measurement with respect to the loading amount of the colored toner. An acquisition means for acquiring a correction amount of a first density value of the colored toner image measured by means or a correction amount of a target value of the first density value, and
Using the correction amount for the colored toner acquired by the acquisition means, the density value or the density value measured by the measuring means of the image formed by the special color toner which is any of the white toner, the clear toner, and the toner containing the metal pigment. A correction means for correcting the target value of the concentration value and
An image forming apparatus equipped with. The correction means converts the correction amount for the colored toner acquired by the acquisition means into a correction amount for correcting the reading error of the density value that occurs when the image formed by the special color toner is measured by the measurement means. The image forming apparatus according to claim 1, wherein the density value measured by the measuring means of the image formed by the special color toner or the target value of the density value is corrected by using the correction amount for the special color toner. The acquisition means is provided with a first reading characteristic indicating a correspondence relationship between the density value of the image of the colored toner measured by the measuring means and the amount of the colored toner loaded on the paper, and the measuring means in advance. The image forming apparatus according to claim 1 or 2, wherein the correction amount for the colored toner is acquired from the difference from the second reading characteristic indicating the correspondence relationship. The measuring means measures the density value of an image from the intensity of the reflected light reflected by the image.
The acquisition means uses the difference between the first reading characteristic and the second reading characteristic in which the density of the image measured by the measuring means is normalized by the specular reflection component and the diffuse reflection component of the reflected light. The image forming apparatus according to claim 3, wherein the correction amount for the colored toner is acquired. The image forming apparatus according to any one of claims 1 to 4, further comprising a detecting means for detecting the amount of the colored toner loaded on the image transferred to the paper. The correction means uses the correction amount of the special color toner obtained by multiplying the correction amount of the colored toner measured by the measuring means by a predetermined coefficient according to the type of the special color toner, and uses the special color toner. Any one of claims 1 to 5 for correcting the output value of the measuring means with respect to the density of the image formed in (1) or the output value of the measuring means with respect to the target value of the density value of the image formed with the special color toner. The image forming apparatus according to the section. A plurality of the measuring means are provided.
The acquisition means acquires the correction amount for the colored toner measured for each measurement means for each measurement means.
The measuring means is obtained by multiplying the correction amount for the colored toner measured for each measuring means by a predetermined coefficient corresponding to the type of the special color toner measured by each of the measuring means. Using the correction amount for each special color toner, the output value of the measuring means with respect to the measured density of the image formed with the special color toner, or the target value of the density value of the image formed with the special color toner measured. The image forming apparatus according to claim 6, wherein the output value of the measuring means is corrected for each measuring means. An image forming program for causing a computer to function as an acquisition means and a correction means of the image forming apparatus according to any one of claims 1 to 7.

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